The present invention relates to a semiconductor device, and more particularly, to a semiconductor device of a static random access memory (SRAM) having a multiport memory.
In a multiport memory cell, the bit lines or word lines of each port tend to be adjacent to each other. Thus, a coupling capacitance between wires may cause crosstalk, leading to a malfunction.
For example, Japanese Unexamined Patent Application Publication No. 2000-12704 proposes a method of avoiding interference between a writing word line and a reading word line by providing a GND wire for the word lines. Similarly, Japanese Unexamined Patent Application Publication No. 2000-236029 proposes a method of avoiding interference between word lines by providing a GND wire between the adjacent rows of a memory cell.
In these methods, however, the shield wire is provided between the word lines and thus the word lines need to be sufficiently spaced. If the word lines are initially spaced in a memory cell, the provision of shield wires does not increase the area of the memory cell.
Moreover, in the technique of Japanese Unexamined Patent Application Publication No. 2009-76931, two word lines adjacent to an unselected word line are not simultaneously selected (activated) because of the pattern of the word lines.
However, the word lines of both ports are not adjacent to each other also in this configuration, thereby less effectively reducing coupling noise between selected word lines.